The present invention relates to a novel process for preparing 5-(2-thienyl)hydantoin, and more particularly to a process for easily preparing 5-(2-thienyl)hydantoin of high purity in good yields by reacting glyoxylic acid, urea and thiophene in the presence of an acid.
5-(2-Thienyl)hydantoin is a useful starting material for preparing D-thienylglycine which is a sort of D-.alpha.-amino acids and is employed for preparing semi-synthetic penicillins and semi-synthetic cephalosporins.
Hitherto, it is known that 5-(2-thienyl)hydantoin is synthesized by the reaction of 2-thiophene aldehyde, ammonium bicarbonate and sodium cyanide according to the Bucherer-Berg's method (U.S. Pat. No. 3,271,389). However, this method requires the use of dangerous sodium cyanide, and further the obtained crude hydantoin is contaminated by by-products caused by the oxidative side reaction of thiophene aldehyde.